f2fs: fix typo

Fix typo and some grammatical errors.

The words "filesystem" and "readahead" are being used without the space treewide.

Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 73690ce..40cfe76 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -758,7 +758,7 @@
 	}
 
 	/*
-	 * POR: we should ensure that there is no dirty node pages
+	 * POR: we should ensure that there are no dirty node pages
 	 * until finishing nat/sit flush.
 	 */
 retry_flush_nodes:
@@ -941,7 +941,7 @@
 }
 
 /*
- * We guarantee that this checkpoint procedure should not fail.
+ * We guarantee that this checkpoint procedure will not fail.
  */
 void write_checkpoint(struct f2fs_sb_info *sbi, bool is_umount)
 {